The invention relates generally to X-ray localizer light for visual marking of a target area to be exposed to X-rays.
An X-ray system typically includes a collimator for establishing an exposure area to the X-rays. The collimator typically includes two pairs of blades made of X-ray absorbing material, such as lead, which can be opened and closed to establish the X-ray exposure area. Because the X-ray beam is not visible to the eye, an X-ray localizer light system is typically provided for supplying visible light from a lamp to visually indicate the exposure area. To accurately represent the area of X-ray exposure at all distances from the collimator, the light and X-ray sources are positioned at substantially the same respective distances to at least three points on a flat optical mirror which are not in a straight line and which cause the visible light to be coincident with the X-rays. Thus, the light source does not have to be in the path of the X-ray beam.
Precise alignment of the distance to the light source and the angle of the mirror are important to achieve coincidence of edges of the visible light and X-ray exposure areas. The primary challenge with conventional approaches has been adequate illumination with satisfactory edge contrast associated with the collimator blades.
Low voltage quartz-halogen projector lamps with high filament temperatures have been used. Such projector lamps have relatively small filament size and high lumen output (e.g., 5000 lumens), offering adequate edge contrast and illumination at the target area. These projector lamps typically also withstand repetitive on/off switching and cost significantly less than high intensity discharge (HID) lamps. However, due to the inherent tradeoff between lumen output and filament life in halogen lamps, these projector lamps typically have very short life (about 300 burn hours or less).
In X-ray collimator applications, lamp replacement involves precise optical alignment and is a task performed by a qualified service technician. The more frequently that a lamp needs to be replaced, the higher the incidence of down-time and labor costs.
It would therefore be desirable to improve localizer lamp life in X-ray collimator applications while maintaining or exceeding conventional performance characteristics of localizer light systems.
Briefly, in accordance with one embodiment of the present invention, an X-ray localizer light system comprises: a long life X-ray localizer light source; an optical concentrator, the light source being situated at a first focal spot, the optical concentrator being configured for concentrating X-ray localizer light from the light source to a second focal spot; and an opaque shield having an aperture therein, the aperture being situated proximate to the second focal spot and being of such a geometrical shape so as to maximize light throughput while meeting light field edge contrast requirements of the X-ray localizer system.
In accordance with another embodiment of the present invention, a light system comprises: a light source; a reflector having first and second focal spots, the light source being situated at the first focal spot, the reflector being configured for concentrating X-ray localizer light from the light source to the second focal spot; an opaque shield having an aperture therein, the aperture being situated proximate to the second focal spot, wherein the reflector comprises a quasi-ellipsoidal portion, wherein the light source is situated within the quasi-ellipsoidal portion, a cylindrical portion situated between the quasi-ellipsoidal portion and the shield for reflecting stray light from the quasi-ellipsoidal portion in the direction of the shield, a back reflector portion situated proximate to the shield, and a centrally-mounted portion situated between the aperture and the light source for directing back-reflected light in the direction of the aperture.